warn for unsupported key in dependency matcher

[svlandeg]

Follow-up to #12926.

Description

The Dependency Matcher only supports 4 specific keys in the (sub)pattern dictionaries. While it may be reasonable to assume that e.g. 'OP' is supported, it's not, and currently this would be entirely ignored if you do try to specify it. Instead, this PR ensures a warning is printed:

UserWarning: [W126] These keys are unsupported: OP, FOO

Types of change

UX enhancement

Checklist

• I confirm that I have the right to submit this contribution under the project's MIT license.
• I ran the tests, and all new and existing tests passed.
• My changes don't require a change to the documentation, or if they do, I've added all required information.